These days, a large number of communications are conducted by optical fiber. A photo-emitter emits a light at the interior of the optical fiber manufactured in a translucent material. The light is then reflected on the internal walls of the fiber and exits at one end where it is captured by a photoreceptor. The fiber does not need to be maintained in a straight line, due to a sufficient reflection index, the light is reflected on the internal walls of the fiber and continues its path to the end.
In another domain, it is necessary to know the deformations of a solid body. For example, the deformation of metal girders is detectable by the variation of the value of resistive nets attached to them. The value of the resistance varies more or less according to the direction of the flexion.
In another domain, compression sensors are known, such as those intended for use on a tactile screen. Layers of compressible substrates constitute a capacitor in which the dielectric constant varies if the intermediate layer is compressed. The substrate layers are deposited onto the lower face of the screen and delimit the areas. The perimeter of these areas appears by a screen print engraved on the screen, or by a displayed line. By connecting the substrate layers to a cluster of detectors, it is possible to detect the area subjected to a pressure.
Recently, flexible screens realized on flexible supports have appeared. The patent application US2006/039031 filed by the Fuji Company and published on the 23 Feb. 2006 describes a camera with a cylindrical cavity. A flexible screen folded around an axis is placed inside the cavity, a rod fixed to the side of the screen allows the user to extract the screen from its compartment and to unfold it in order to make it visible. The photo taken by the camera is displayed on the unfolded screen. The user interface is realized by keys arranged on a rigid part connected to the flexible screen. Among the flexible screen technologies, the OLED (Organic Light Emitting Diodes) screens can be cited. The structure of an OLED device consists in an organic layer stack of a few tenths of a nanometer in thickness. Deposited on a thin and flexible support, such a structure represents a negligible depth and can thus support without damage a deformation consecutive to bending the support. But such a thin structure does not allow it to be equipped with a compressible substrate in order to render such a screen tactile. Nevertheless, the possibility to transmit a command by the simple flexion of the screen offers great navigation possibilities. As cited previously, it is known to stick resistive nets onto the flexible material. But the adhesion of resistive nets to the back of a flexible screen requires realization of the connection paths to connect them to the detectors of changes in resistance. The screen and resistive nets assembly then becomes fragile.
The document WO 2005/026938, published on 24 Mar. 2005 describes a flat tactile screen on which a user has exerted a pressure. Cells emit beams perpendicular to the surface of the screen. The user approaches his finger to the area considered, which has the effect of reflecting the light beam which as a result is propagated in the transparent substrate. A detector placed on the side enables detection of the position of the finger, this detector is for example a CCD line placed in front of lenses. Numerous detection techniques are used to determine the position of the area where the reflection is produced. All of these techniques consist in arranging a plurality of beam emitters to detect if the user is exerting a pressure in a determined area or not. These techniques impose utilization of a multiplicity of emitters and associated detectors, which results in high cost if the surface susceptible to be pressed is large.
The present invention proposes another way to detect the flexion of a screen with an improved reliability.